Method for production of a helical spring from a fiber-reinforced plastic

Abstract

The invention relates to a method and an apparatus for the production of a helical spring from fiber-reinforced plastic, where a strand of fibers and plastic resin is wound onto a rotationally symmetric rotor provided with a spiral groove then hardened and finally removed from the rotor. In order to be able to produce helical springs with desired and in particular circular cross sections of the strand with small tolerances of the shape, a stator with an inner spiral groove is surroundingly disposed around the rotor, which spiral groove together with the spiral grooves of the rotor form the cross-sectional profile of the strand, where the rotor and the stator relative to the rotation of the rotor are shifted axially with respect to each other in an amount corresponding to the slope of the spiral grooves.

I claim: 
     
       1. A method of making a helical spring which comprises the steps of: rotating an inner cylindrical member formed with an outwardly open helical groove around the axis of said member;   enclosing said inner member in an outer member formed with an axially extending bore provided with an inwardly open helical groove registering with the outwardly open helical groove to define a closed cross section for a spring to be formed in said grooves;   feeding a strand of fiber reinforced synthetic resin in a plastically deformable state into said outwardly open groove thereby entraining said strand into said outer member and molding said strand to said cross section between the grooves of said members; and   axially shifting said members relatively corresponding to the pitch of said grooves during the rotation of said inner member whereby a spring formed from said strand emerges from said outer member on said inner member at an end of said outer member opposite that at which said inner strand was entrained into said outer member.   
     
     
       2. The method defined in claim 1, further comprising the step of hardening said strand at least partially within said outer member. 
     
     
       3. The method defined in claim 2 wherein said strand is produced by winding fiber around a core and impregnating the fiber wound around said core with a thermosettable synthetic resin material before said strand is introduced into said outwardly open groove. 
     
     
       4. The method defined in claim 1, further comprising the step of introducing a nonhardening rinsing liquid between said members for rinsing away excess material from said strand. 
     
     
       5. The method defined in claim 4 wherein said rinsing liquid is a nonhardening synthetic resin miscible with synthetic resin of said strand.